The present invention relates an elastic yarn feeding apparatus for use in knitting machines. In particular, the present invention relates to an elastic yarn feeding apparatus that is capable of feeding threads to knitting machines without applying tension to the threads.
Fabrics with soft, elastic texture are favored by people seeking high quality dresses. To make such fabrics, it is an important factor that, when feeding threads to the knitting machine, no-tension be applied on the threads. Should this be the case, although the knitted fabric may look flat and smooth in surface during the knitting process, the same fabric, however, after the knitting process is completed and the tension is removed, would become somewhat wrinkled due to the restoration of the stretched threads. The wrinkle on the surface of fabrics would exhibit a displeasing look.
A conventional no-tension yarn feeding apparatus is disclosed in German Patent Application No. P 32 33 869.4 (Taiwan Application No. 7228832), in which the bobbin holding the yarn is placed on and supported by a pair of horizontally extended driving rollers. Yarn feeding without applying tension to the threads is achieved by driving the two driving rollers to allow the circumference of the yarn wound around the bobbin to come into contact with the two rollers. This apparatus, although simple in structure and easy to operate, has the following drawback. In the apparatus, the distance between the two driving rollers (measured from the center axis of each roller) is fixed. This causes no problem in the beginning stage of supporting the bobbin for steady rotation. However, in the final stage of the knitting process when the yarn wound around on the bobbin is reduced due to consumption, the reduction in weight of the yarn would cause the bobbin to quiver and rotate in unstable speed. This may even cause the bobbin to jump off the supporting rollers, thereby interrupting the knitting process.
To prevent quivering and instability in speed of the bobbin from taking place, the bobbin along with the remaining yarn is replaced with a new roll of yarn at a certain point in the final stage. The remaining yarn on the bobbin is thus wasted. Operators of the knitting machine thus often have to pay high attention to watch for the undesired conditions in the final stage of the knitting process so as to make the replacement promptly. This causes a waste in the material and thus high fabrication cost.